Field of the Invention
The invention relates to an amplifier with adjustable gain, and particularly relates to an amplifier with adjustable gain applied to a high-speed transmission interface.
Description of Related Art
In a conventional technical domain, an amplifier applied to a high-speed transmission interface has a negative feedback resistor, and in an adjustment operation of a direct current (DC) gain of the amplifier, the negative feedback resistor is accordingly adjusted, and a high-frequency peaking of the amplifier is accordingly varied. FIG. 1 is a frequency response diagram of a conventional amplifier. In FIG. 1, a curve 101 has a higher DC gain compared with that of a curve 103, and a resistance value of the negative feedback resistor of the amplifier working under the curve 101 is smaller than a resistance value of the negative feedback resistor of the amplifier working under the curve 103.
According to FIG. 1, it is clearly known that regarding the amplifier working under the curve 103, a gain value of the amplifier corresponding to a frequency FH1 is greatly varied compared to the DC gain of the amplifier corresponding to a low frequency. Namely, the conventional amplifier working under a low DC gain state may have a large high-frequency peaking variation.